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Thread: Help with a Decwriter III LS-120

  1. #1

    Default Help with a Decwriter III LS-120

    Hello, I recently bought a Decwriter III LS-120, and after cleaning it up and making sure the voltages were correct and stable, I tried printing on it, it worked, but there was one line that was not working, by that I mean on the surface of the print head, there are the 7 small dots that push out to create the letters, and one of the dots are not pushing out.

    Should I start with inspecting the print head itself, or is this a problem that resides in the controller board for the print head?

  2. #2

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    I would check if the coil is not shorted by measuring the resistance of each coil of the head.
    If they are all ok, then it's likely one of the driver transistors is broken.

  3. #3
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    It could also mean that the pin is sticking in the printhead due to dried up ink or dirt. Worth inspecting the printhead also.

  4. #4
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    Quote Originally Posted by PG31 View Post
    It could also mean that the pin is sticking in the printhead due to dried up ink or dirt. Worth inspecting the printhead also.
    This is where I would start. Clean the head. It's not such an uncommon problem.

  5. #5

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    Hello, I've cleaned the head, and the problem is still there, I've also tested the continuity from the power board to the print head and everything is ok. So I suspect this has something to do with the driver transistors

  6. #6
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    Quote Originally Posted by Nick7928 View Post
    Hello, I've cleaned the head, and the problem is still there, I've also tested the continuity from the power board to the print head and everything is ok. So I suspect this has something to do with the driver transistors
    If cleaned and you still have the problem, then yes. Check coils and transistors.
    (But I hope you let the head soak in alcohol for at least 24h. The gunk can be really sticky!)

  7. #7

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    Hey everyone, I soaked the head in alcohol for 48 hours just to be sure, and sure enough, it turned out to be a stuck head. Thanks for the help guys!

  8. #8
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    You will be amazed just how much ink a print head will pull into the pin sleeves over decades of use and storage.
    [Need something to waste time on? Click here to visit my YouTube channel CelGenStudios]
    --------------------------------------------------------------------------------------------
    [No time for videos? Click here to visit my Twitter feed @CelGenStudios]

    = Excellent space heater

  9. #9
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    Quote Originally Posted by Nick7928 View Post
    Hey everyone, I soaked the head in alcohol for 48 hours just to be sure, and sure enough, it turned out to be a stuck head. Thanks for the help guys!
    Excellent! Happy to help.

  10. #10
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    Quote Originally Posted by NeXT View Post
    You will be amazed just how much ink a print head will pull into the pin sleeves over decades of use and storage.
    Oh, I would

    Just been fighting with a LA100 Letterwriter.

    Mind you , it has been in service at work for 32 years and we still use it !.

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